In fiber optic communication systems it is often desirable to reconnect one end of an optical fiber line to a replacement transmitter or receiver or to a line diagnostic device such as a time domain reflectometer. Optical fiber switches enable this reconnection to be accomplished from a remote point without the need for a craftsperson to perform this task by manually exchanging fiber optic connectors or splices. One principal class of optical fiber switches is the moving prism type in which the switching action results from the repositioning of a transparent reflecting and/or refracting prism in two or more parallel beams so as to cause the light travelling in the beams to change its course between sets of input/output fibers, coupled to the beams by lensed devices. U.S. Pat. No. 4,634,239 dated Jan. 6, 1987, having the same inventor and assignee as the present invention, is hereby incorporated by reference into the present application. In that disclosure, a multiple port optical fiber switch is described which uses a hexagonal prism design particularly well-suited for this type of fiber optic switch. The switch has a central beam coupled to input and output fibers by lenses and has eight similarly coupled parallel beams symmetrically spaced around the central beam. On each of the eight beams is one hexagonal prism through which it passes undeflected until the prism is repositioned by a radially inward motion, and this results in the exchange of light between the central beam and the one beam from which the prism was moved. Only one prism may be so activated at a time. Although the switch described in U.S. Pat. No. 4,634,239 presents a clear advantage over the prior art, it would be a still further improvement if the number of prisms could be reduced, resulting in a simpler operation and a lower cost switch.